Singlet oxygen is an activated form of molecular oxygen. Various compositions that generate singlet oxygen in the presence of light and oxygen (and in some cases in the presence of a photosensitizer) have been used as photobleaches or as bleach activators. References describing such compositions include U.S. Pat. Nos. 5,679,661, 5,795,854, 5,891,838, 5,904,734, 5,916,481 and 6,262,005, European Patent Application No. EP 0 845 524 A2 and Japanese Published Patent Application (Kokai) No. JP 6-041593. Other references relating to singlet oxygen include Aubry, J. M. and Bouttemy, S., “Preparative oxidation of organic compounds in microemulsions with singlet oxygen generated chemically by the sodium molybdate/hydrogen peroxide system”, JACS, 119, 5286–5294 (1997) and Gorman, A. A. and Rodgers, M. A. J., “Lifetime and reactivity of singlet oxygen in an aqueous micellar system: a pulsed nitrogen laser study”, Chem Phys. Lett., 55, 52–54 (1978).